The present invention relates to the art of earth boring and more particularly to a removable nozzle for bits that use a drilling fluid which is jetted downwardly toward the cutting operation carried on by the cutters against the bottom of the hole. More particularly, the invention relates to the provision of a fluid nozzle for the drilling fluid which may be easily installed, or replaced by a nozzle of different size or internal contour.
The bit to which the invention relates may be of any conventional form wherein the drilling fluid is pumped to the bit for direction by a nozzle downwardly from the bit. It is customary to provide a nozzle structure which is of different material than that used for the body of the bit itself. The nozzle is usually of material which is highly resistant to wear such as cast tungsten carbide, sintered carbide or a ceramic material. A problem has been encountered in securing such nozzles in place and yet allow the nozzle to be easily removed and/or replaced.
Replaceable nozzles have been developed in the past. These nozzles have been retained in a fluid discharge bore in the bit body by abutting their upper ends against shoulders in the bore and then inserting snap rings into grooves at the lower end of the nozzle or a retainer element bridging between the nozzle and the bit body. The drilling fluid is very abrasive, and the exposure of the snap ring as well as the bit body at the lower end of the nozzle adjacent the snap ring groove to the wash of the drilling fluid has caused this snap ring as well as the body portion supporting it to erode and fail, permitting the nozzle to be lost into the bottom of the hole. This structural arrangement, wherein the snap ring and its support are continually exposed to drilling fluid, together with the fact that higher drilling fluid jet velocities and consequently high pressure differentials across the nozzle are being used, combine to make the snap ring somewhat unsatisfactory in many cases for retaining nozzles in the bit body. The retaining element occasionally becomes stuck in the matching grooves and difficulty is encountered in removing the retaining element.